This is a measure in grams of how much water/sweat vapour can pass through a square-metre of the garment's fabrics in a 24 hours. So in this case the fabric can pass approximately 5-litres liquid as vapour.

5000 g/m²/24h would be considered good breathability - suitable for a range of activities where sweating will be moderate, with peaks of higher perspiration output.

Waterproof 5k

Garment rated at 5000mm waterproof.

This means in a static column water resistance test a 1-inch diameter column of water 5 meters high was poured onto this garment without the water penetrating the fabrics/materials.

5,000mm waterproof would be considered good waterproofing - resistant to rain, sleet and snow showers. However, this level of waterproofing might prove susceptible to water ingress under pressure (e.g. prolonged kneeling on wet ground), prolonged contact (e.g. brushing with wet foliage) or submersion (e.g. standing in a stream).